


Human Intercourse

by SpyroForLife



Series: PMaZR Hidden Identity fics [1]
Category: Invader Zim
Genre: Blindfolds, Clothed Sex, Feelings Realization, First Time, Gratuitous Animal Facts, Grinding, M/M, One Shot
Language: English
Status: Completed
Published: 2019-08-28
Updated: 2019-08-28
Packaged: 2020-09-28 07:40:24
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,321
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20422340
Author URL: https://archiveofourown.org/users/SpyroForLife/pseuds/SpyroForLife
Summary: Zim and Professor Membrane may be dating, but Membrane has no idea Zim's an alien, a deception Zim intends to maintain for as long as possible. But when he realizes the value humans place in 'intercourse' in a relationship, he decides he needs to try it. Which means he needs to be clever about how he keeps Membrane from discovering their biological differences...





	Human Intercourse

**Author's Note:**

> Based on this lovely, somewhat lewd, but quite sweet PMaZR comic by TheLuckyestClover7 on Tumblr! https://theluckyestclover7.tumblr.com/post/187251931057/a-trash-fire I really like how Zim is portrayed just absolutely falling for Membrane over the course of it and I wanted to do a fanfic version. :D Hope you enjoy!

Zim was just about ready to go visit Professor Membrane, but first he wanted to do a little more research to help him keep up his ruse. So far Membrane had no idea he was an alien or even that he was his son’s rival! No, a drawn on goatee and some eye shadow was all it took for Zim to convince Membrane he was an entirely different person.

And after spending time with the other at the lab, showing off his vast knowledge of science and lavishing Membrane with compliments, he had finally managed to begin dating the man. His plan was going smoothly, but he had to ensure Membrane stayed interested. They were at a comfortable point now, holding hands in public and regularly snuggling up on the couch while hanging out at Membrane’s house, but Zim wanted to take things further. He wanted Membrane to be utterly devoted to him.

So here he was, searching his computer for information on what humans expected out of relationships.

Everything seemed in line with what he was already doing. Regularly seeing each other, engaging in physical contact, talking and getting to know each other… engaging in intercourse… wait, what?

Zim’s face grew hot as he clicked the link. Of course he was familiar with the concept, plenty of species relied on sexual intercourse for reproduction, it was simply outdated for irkens due to the efficiency of cloning. He’s personally never tried it nor did he have an inclination to. But…

He scanned over the page, reading about how relationships needed a healthy sex life. Needed? Surely not everyone needed that. He knew he didn’t.

He scrolled down to the comment section. One person had written, ‘Laughs in asexual.’ There were a couple upvotes for it.

But most of the comments were in agreement that a relationship just didn’t have that spark if there wasn’t sexual attraction.

Zim’s eyes widened a bit with concern as he saw how many humans agreed. He kept reading comments.

‘I feel like sex _is_ important in a relationship...’

‘I can’t see having a boyfriend without sex.’

Zim straightened, heart racing. If that was the consensus… he needed to do more research. He didn’t want Membrane to leave him because of this.

He grabbed for the mouse and did a new search, this time specifically for human intercourse. He eyed several questionable links before just deciding to check the Wikipedia page. He skimmed over it, brow furrowing as he read about how humans reproduced. Then he found diagrams of the relevant sexual organs.

He jerked back upon realizing how different they looked from his. Functionally he was similar to a human, sure, but when it came to appearances… he wasn’t at all the same. And that would be obvious if he engaged in intercourse with Membrane.

He went back to his search, deciding to brave one of the sketchy sites. It was full of ads and straight up showed him a video of two humans mating. He gagged and covered his mouth, pausing the video. Then he sighed and looked away. Well, he could still try it, but how to keep Membrane from realizing he wasn’t human?

His computer dinged as he got a popup for a different porn video. He rolled his eyes and reached to close it, then paused when he saw that it showed a smiling man with a blindfold on, who seemed rather pleased with his situation. And that gave Zim an idea. “Ooh, that could work.” If wearing a blindfold during sex was a kink… he would try it.

He checked the time and stood, turning off his computer and going to check some of his supplies. It took some searching, but finally he found a strip of black fabric that would work. He slipped it into his pocket, double-checked that his disguise looked good, and headed out.

He and Membrane had the house to themselves tonight, for once. Gaz was spending the night with a gamer buddy for the release of a new game and Dib had gone camping in yet another attempt to find Bigfoot. Zim snickered, knowing that he really just wanted to stay away because he was still disturbed by his dad dating his enemy. Which was why Zim was doing this anyway, but he had to admit, he was starting to genuinely like Membrane and he enjoyed spending time with him outside the lab.

The feelings were odd, but he went with them. It wasn’t really a big deal, he just respected the man was all, it totally wasn't going to blossom into something more. He wasn't in that deep.

When he reached the house, he let himself in. “Membrane?” he called.

“Right here, honey!” Membrane replied, sitting up and waving from the couch.

“Ah!” Zim felt the usual smile cross his face, he couldn’t help it, everytime the other called him ‘honey’ he just got tingles and the world seemed just a little bit brighter. He went to join him, sinking down next to him and leaning in close. “How was your day?” he asked.

“Great! Work at the lab was rather slow today, so I caught up on a lot of personal projects. And with both kids out of the house, I can watch whatever shows I want!” Membrane gestured to the TV.

Zim saw it was on Animal Planet. “Ooh, what’s this show?”

“The Most Extreme, it’s fascinating, they do top ten lists of animals based on certain traits. Strongest bite, most venomous, and so on. This episode is called Workaholics and it’s about the hardest working animals. Obviously the list is subjective but it’s still a good watch.”

“I see.” Zim watched curiously, and Membrane offered to grab them some tea. Zim agreed and the other got up to go make it.

Alone in the living room, Zim’s thoughts quickly strayed away from the show. How was he going to bring up intercourse? How did humans ask for it? Oh, he should have researched further, what if there was a courtship ritual? Irkens did a whole display in the old days to ask a partner to mate. But humans didn’t seem as dramatic. He struggled to remember how the humans in movies did it. He’s unintentionally stumbled across such scenes in a few films, and it seemed to take very little for them to go from kissing to throwing themselves into bed together. So maybe it was as simple as just… asking. Bluntly.

He made up his mind to do so when Membrane walked back in holding two mugs of hot water, sitting down and passing one to Zim. He set an assortment of tea on the coffee table, and Zim chose a mint tea and dropped the bag into the cup to steep.

Membrane chose a green tea and dipped it in his mug, and for a while the two watched the show in companionable silence. It was on the fifth animal of the countdown, the beaver.

Zim didn’t care for many aspects of Earth, but the animals were fascinating. There were so many and they were so diverse, with their own unique behaviors and cultures.

“They really are good engineers, aren’t they?” Zim asked as the narrator explained how beavers can dam rivers, creating lakes, and how the creatures were always ready to respond to and repair leaks in their structures.

“Yes, they’re brilliant! Such bright little creatures, and very cute too.”

Number four was a bird known as a megapode. Apparently it spent eleven months of the year moving earth every day to make a nest for its eggs. The resulting mounds were often huge, some reaching diameters of fifteen meters and weighing almost fifty tons! The males spent so long working just to keep the nest ready for breeding season.

“Amazing,” Zim commented. “Such commitment.”

It went to a commercial after that, and Membrane explained that after the break will be three and two, and yet another commercial break before they finally reveal the number one animal.

“Of course, gotta build the suspense,” Zim said.

“I’ve seen this episode before though. Want to know the final rankings?”

“Sure.”

“Number three is the cleaner fish that constantly cleans the scales and mouths and whatnot of other fish, and it can eat over a thousand parasites in a single day!”

“Wow!” Zim exclaimed. “Gross, but wow! What a job, eating parasites all day…”

“Indeed. Number two is the leafcutter ant, they basically form assembly lines and work together to turn leaves into a food they can all eat. The adult ants eat sap from the leaves, but they also use the leaves to cultivate fungus! The fungus relies on ants for survival, and in return produces these nutritious structures called hyphae that the ants harvest and feed to their larvae. Their society is extraordinarily complex.”

“Huh, so they basically farm,” Zim commented.

“In a sense, yes. It’s a sort of mutualism between the ants and the fungus. I’ve dabbled in zoology but haven’t gone too in depth with entomology. The insect world is huge and complex. I respect every scientist who has devoted their lives to studying it.”

Zim nodded, humming curiously. “Yes, sounds like quite a task. And the number one workaholic? Besides you, of course?”

Membrane chuckled at that. “Why, the humble bee, of course.”

“Bees?” Zim couldn’t help but tense. He had a bit of a love-hate relationship with those creatures. They looked cute and fuzzy, but they were terrifying in a swarm and he was very aware of their stinging capabilities.

“Yes, bees work very hard! Much harder than me! They’re basically working from the moment they’re born! Sure, they spend some time as larvae within a honeycomb, but once they’re done pupating and leave the comb, they’re immediately tasked to take up cleaning the hive and looking after the younger larvae! A young worker bee moves on to collecting nectar and pollen from foragers when she gets older, and she may be tasked to guard the hive. And eventually she’ll get to go outside and start foraging for herself. Constantly busy! All day, every day! Their work ethic is simply unmatched! To say nothing of how the queen lays an egg a minute. Her job must be hard.”

Zim shuddered just imagining it. “An egg a minute. Ugh.”

“Haha, I know. Imagine if humans did that.”

“I’d rather not imagine.”

The show resumed, going through animals three and two, which were the cleaner fish and leafcutter ant as Membrane had said. Zim watched with fascination, taking sips from his tea but finding it too hot to drink much of, so he mostly just held it and enjoyed the warmth seeping through his gloves.

The narrator began hyping up the most extreme animal… and then went to commercial just as Membrane said would happen.

Zim sighed and snuggled back against Membrane, figuring now was as good a time as any to propose sleeping with the other. So, casually playing with the string of his teabag, he said, “Hey, do you want to try intercourse?”

Membrane sat up a bit, coughing on his tea. Zim glanced at him and saw that his face seemed a bit red, though the collar and goggles made it hard to tell. He cleared his throat and replied, “W-what?! Well, I didn’t even think-”

“Well I do,” Zim stated, letting go of the teabag and taking a long sip.

“Wait, really?” Membrane seemed surprised.

Zim wondered if maybe it was a little soon to ask about this, but oh well, he wasn’t backpedaling now. “Uh, yeah,” he said as if it was obvious.

Membrane sat forward and set his mug down. “Sorry, you just hadn’t brought it up until now, I figured you were fine not doing that, but if you want…”

“I do, I really want,” Zim assured him. “Though, one request. Think we could make it a little, er… spicy?” He slipped the blindfold out of his pocket.

Membrane definitely blushed at that, and Zim blushed too at seeing how flustered the man was. “Oh? Well, I don’t see why not…” He glanced at the TV, then back at Zim. “Did you want to do it now, or wait until the show’s over?”

“Eh, you already told me how it ends, but if you want to see the rest…”

“No, I’m alright, like I said I’ve seen this before.” Membrane stood, offering Zim his hand. “Well? Shall we go?”

Zim’s heart was beating somewhere in the base of his throat, but he shoved his reservations aside and stood too, taking Membrane’s hand. “Yes.”

He followed the other to his bedroom, and while Membrane slid his boots off, Zim was mildly amused to see him hop into bed and lay back with the rest of his clothes on. Then again, humans seemed to like unclothing each other for sex. So Zim copied him, only taking his boots off before joining him. He offered him the blindfold, and Membrane took it with a soft laugh, tying it over his eyes. Then he rested his head back against a pillow and Zim carefully moved to sit on his lap.

Okay, here he was. Ready to do human intercourse with his partner. He wasn’t nervous. Of course not. The flush in his cheeks was just… it was warm in here. Of course.

Membrane was still fiddling with the blindfold, and finally he said, “Don’t you think this is a bit much?”

“Nah,” Zim answered, laughing a bit too loudly. He coughed and got a hold of himself, staring down as he placed his hands on the other’s sides. Okay. As long as Membrane couldn’t see anything, it would all be fine. The Internet said he should start slow, and while he may not know what exactly he was doing, as long as Membrane kept the blindfold on, it would all be fine…

He was startled from his thoughts by Membrane speaking, reaching up to hold him. “Uhh, honey? If you’re nervous we don’t have to do it.”

Zim’s stomach did a flip and his blush spread, oh the other was so caring and it got to him. “I want to! Do it, I mean! I’ve just never done this before.” He anxiously tugged at his collar, very aware of how nice Membrane’s hands felt holding his hips, firm enough to be comforting but not enough to make him feel trapped.

Membrane lifted his head, saying, “Is the blindfold necessary?”

“I guess not,” Zim relented. If the other was going to have to guide him through this, he supposed it would be good for him to see what he was doing.

“Good.” Membrane quickly untied it and pulled it off, giving Zim a heated stare. “Because I want to see your face.”

_ Oh_. That simple confession went right to Zim’s heart, an entirely new sensation rearing its head. There were flutters in his belly and he found himself groaning with the sudden desire to hold Membrane close and never let him go.

Membrane’s strong hands suddenly shifted him, pulling their groins together until they rubbed in quite the tantalizing manner. “And don’t worry, we don’t have to go all the way tonight,” Membrane continued.

Zim bit his lip at the unfamiliar sensation between his legs, and when Membrane pulled him into a slow grind, Zim couldn’t help but arch, gasping in pleasure.

“There we go,” Membrane purred, watching him intently.

It was nearly overwhelming how good that simple motion felt, and Zim panted as he gave in to it, exclaiming, “I didn’t know it would feel like this!” He held onto Membrane’s wrists, heart swelling with affection for the other.

Membrane chuckled, eyes bright as he enjoyed Zim’s reaction. He pressed his hips up against him, brushing his coat open so there was one less layer between them, and Zim eagerly responded, his pupils large and eyes falling to half mast as he got into a gentle rhythm moving with the other.

It was unlike anything he’s ever felt, sending pleasure coursing through his body, and heat pooled between his thighs. He gazed down at Membrane, seeing that the other seemed entranced by his movements, watching him closely.

It took Zim a few attempts to speak, and when he finally managed to, his voice had gone breathy and slightly hoarse. “I w-want to see your face too.”

“Of course, love.” Membrane lifted a hand to his face, unhooking his goggles and sliding them off. He left them on the bed next to him, then unbuttoned the top of his coat and folded it out of the way, letting Zim see his smile. The human was clearly enjoying this, his cheeks flushed and eyes heavy with lust. Zim gulped at the raw desire on the other’s face, his body giving a pleasant shudder that went all the way up his spine and made his toes curl. He understood now why humans liked this. Sharing this kind of intimacy with another person… it was incredible.

He began to notice a firmness under him, and intentionally rocked himself against it, an unsteady gasp escaping him. Membrane moaned in response, fingers twitching before beginning to feel up under Zim’s shirt.

So this was arousal, Zim thought hazily. It was new and almost frightening, his body feeling hot and tense, but in a good way. His shaft, usually kept withdrawn in a protective sheath, was now pushing itself out, straining against his pants as he grinded with the other. He didn’t know it was this sensitive, and sweat beaded at his temples as he pressed his hips forward and back. His thoughts wandered, his eyes slipping shut as he imagined what it could be like to go “all the way” as Membrane had put it. He assumed that was the penetrative sex he had read about earlier. It had sounded uncomfortable, but now that he was here on Membrane’s lap and feeling him so intimately between his legs, he realized that he wouldn’t mind such a thing. He was so wet he could feel it slicking against the inside of his pants, his insides seeming to ache for touch. And judging from the size of that bulge under him, Membrane would fit so snugly and perfectly in him.

He whimpered softly and heard Membrane groan quietly in response, rubbing gentle circles against his hip bones. “Doing okay?”

“Mhm,” Zim hummed. He tugged slightly on Membrane’s gloves. “Could you um… ohh, that feels so good… nn, could you take your gloves off?”

“Are you sure? After all, my hands are…”

“Robotic, yes, I know. And I think it’s sexy. So lemme feel them.”

Membrane lifted a hand to his face, lightly biting on his index finger and tugging the glove off with his teeth. A moment later and he had snapped the second glove off, tossing both carelessly aside.

Then his hands returned to Zim’s waist and went back under his shirt, and Zim trembled at how strange they felt. The metal slid smoothly against him, but rather than being cool like he expected, they were actually rather warm. And the joints were coated in a kind of silicon, so there were no rough edges to catch on his skin. He relaxed into the other’s hold, sighing with bliss.

Membrane smiled as he felt along his sides, giving gentle rubs. “How’s that?”

“Good. Mm, you feel so good…” Zim held onto Membrane’s hands, using them as an anchor to press himself down more desperately.

It drew a whine from the other, who slid his palms down to Zim’s thighs, spreading them a bit further apart. “Ah, you really are feeling good, aren’t you? If you’d like, we can take things further…”

“No!” Zim said quickly, not wanting him to see their biological differences. He wasn’t letting that cat out of the bag yet. “No, I uh… haha, I just wanna take things slow right now.”

“That’s perfectly fine, just let me know if you want to do something else.”

Zim nodded, and as he picked up his pace, the sensation intensified until it was all he could think about. He kept his eyes shut, his vocalizations growing louder, encouraged by Membrane’s husky pants. His legs shook uncontrollably and his fingers twitched against Membrane’s hands, claws dragging against the metal as he seeked purchase, the sensations were reaching a nearly unbearable level and he wasn’t even sure anymore if what he was feeling was pleasure or pain.

Then, suddenly, it exploded into what he could only describe as a tidal wave of ecstasy. His body spasmed uncontrollably and he cried out, hips jerking and losing their rhythm.

“Ah!” Membrane tightened his grip on Zim’s hips, giving an especially firm grind up against him as he finished too, pushed over by Zim’s cry and the sheer pleasure on his face.

Zim was shaky when he came down from his high, blinking his eyes open and breathing hard. Stray pangs of pleasure radiated up his body and he let a smile cross his face as he laid down on Membrane’s front, crawling up to nuzzle him.

“Wow,” he said dreamily.

“Yeah, wow,” Membrane said breathlessly. He wrapped his arms around Zim and kissed him, and Zim ran his hands through Membrane’s hair as he responded, purring happily. “That was nice.”

“That was more than nice!” Zim exclaimed. “It was amazing!” So amazing he wanted to just throw his wig off and use his antennae to mark Membrane as his mate right now. He blinked, and gave himself a little shake, telling himself not to get that attached. This was all a ploy to get to Dib, remember? He just wanted to embarrass his enemy, he wasn’t actually going to fall for-

“Heh, first times are a little overwhelming, hm?” Membrane asked, rubbing Zim’s back. “But we can do so much more than that. I can make you feel so good. I like seeing you in pleasure.”

Oh fuck, there were those butterflies again. Zim chuckled, flattered and mildly turned on. “Ah? Well, um… I think I’m okay for now, we can um… go further some other night, if that’s okay.”

“Of course it’s okay. I’m not going to rush you, we can do things at whatever pace you’re comfortable with.”

Zim just wanted to rip out his traitorous heart. It actually hurt, how much he wanted the other. Not just physically, but emotionally. He really wanted to be with him. Not just as part of an evil plot, but for real. Membrane cared so deeply for him, and he couldn’t help but feel the same. The man was tall, intelligent, kind… so passionate about his work and a great conversationalist… he was perfect.

“Honey, are you alright?” Membrane asked. “You seem distracted.”

“Hm? Oh, I’m fine, just… tired.” Zim sat back a bit, shifting his legs and making a face as he realized the inside of his pants was drenched in sweat and fluids. It was actually pretty gross, and he immediately wanted to toss everything off and put on fresh clothing.

Membrane seemed to read his mind. “We might want to get out of these sweaty clothes, hm?”

“Ah, yes. But um, I don’t have anything else to wear.”

“I don’t mind you being naked with me.” When Zim tensed at that, he quickly continued, “But I can get you a shirt to use as a nightgown if you like.”

Zim relaxed at the suggestion. “Yes, that’ll do.”

They climbed out of bed, and Membrane went over to the closet, grabbing a shirt and offering it to Zim. It was a large promotional shirt for Membrane Labs, and looked like it was a little big even for Membrane himself. Zim waited until Membrane was turned away tugging his own clothes off, and quickly tossed off his uniform and slipped the big shirt over his head. It was much softer than his uniform, and the hem went down his thighs, nearly reaching his knees. He rubbed his arms, feeling weird without his gloves, and picked up his clothes to set on the dresser out of the way.

When he turned around, he saw that Membrane had disrobed and was now pulling on fleece pajama pants with tiny atom decals all over them.

Zim let out a giggle-snort, and Membrane smiled, giving his leg a pat. “Dib bought me these for Christmas one year. They’re very comfortable, if a little garish.”

“I love them,” Zim replied. He especially loved that Membrane wasn’t wearing a shirt with them, so he could appreciate his strong chest and the full length of those robotic arms. He hurried over to join him as he climbed back into bed, getting under the covers. Membrane held an arm out and Zim flopped right onto it, smiling as the other scooped him close and turned onto a side to spoon him, enveloping him in warmth. Membrane’s other hand rested gently on his thigh, and Zim felt him nestle his nose into the back of his neck and sigh, smiling too.

“So I take it you’re spending the night?” Membrane asked quietly.

“Of course,” Zim assured him, moving a hand down to Membrane’s and holding it.

The other kissed his neck. “Mm, alright. You want to go to sleep now, or go back out to the living room and watch a movie?”

“Well…” Zim’s thumb traced idly against Membrane’s hand as he considered it. He didn’t typically sleep, but earlier had left him strangely tired. It felt like all his energy had escaped him with that release and he was perfectly content to just lay here and recover. So he said, “I’m pretty tired, I think I’d like to sleep.”

“Alright, me too. Goodnight, then.”

“Goodnight.”

Membrane leaned over him slightly to kiss his cheek. “I love you.”

Zim took a breath and said, “I love you too.” And this time, he meant it. 


End file.
